The London-wide bus strike today is the first for 30 years. It is an offensive strike, in that rather than defending existing conditions the drivers want something more: a bonus of £500 for their work during the Olympic Games. It is also strategically offensive, since part of the aim of the union is to restore collective bargaining across the capital, rather than conditions being decided at the company level.

The significance of this may be lost on London's transport bosses. Most strike actions in recent years have tended to be defensive, attempting to either prevent or mitigate cutbacks. Moreover, the defining context for most industrial action today is the public sector's attempt to defend itself against the Tories' cuts. In this case, however, the vote for strike action over an offensive issue was 94%. The union says the strike is solid, and TFL is warning of serious disruption. This doesn't suggest that the workers are in a timid mood.

What else might the employers be missing? They may have underestimated the potential strength of their opponent. The buses carry 6.5 million passengers every day. London's infrastructure relies on this. Businesses rely on it. Notably, despite Boris Johnson's promise to clobber tube unions, he has been unable to deliver due to the ability of RMT members to bring the capital to grinding halt. Given a sufficient push, the power of bus workers could be just as strong. This would profoundly affect the capital's industrial relations and possibly put the administration in a weak position.

Generally speaking, the employers respond to major strike action with a concerted demonisation campaign. In London, the Evening Standard is their constant supporter in these efforts. But they may find it hard to demonise bus workers, whose demand is reasonable. It is estimated that London will have an extra million people visiting during the Olympic Games, adding a tremendous burden to bus services, and making the job harder. In recognition of this, other transport workers in Network Rail, the DLR and the airways have already obtained a bonus – up to £1,200 in the case of BAA workers. The amount requested is a small share of the existing surplus of £759m, leaving aside the extra income that will be generated by the games. It is certainly modest compared with the £80,000 bonus claimed by the TFL boss Leon Daniels for the Olympics. This may be why a survey of bus passengers carried out for Unite showed that nine out of ten passengers support the strikers' demand.

One other thing they might consider is that despite the courts awarding an injunction against unions to three of the employers, the unions didn't back down and cancel the strike. Instead, strike action has proceeded in the 17 firms unaffected by the injunction, which covers only 15% of bus drivers. The unions are planning to appeal against the injunction.

Of course, this raises the question of the courts and their relationship to industrial disputes. The judge in this case asserted that he believed the statutory procedures would be shown not to have been followed by the union. There is now a long tradition of courts siding with employers on technicalities relating to restrictive anti-union legislation, and employers are taking advantage of this.

Part of the problem is with the laws, which is why the ILO has called for their repeal. But judges have a degree of flexibility in how they interpret law relating to trade disputes, where conflicts often involve minor details of compliance. The fact that the courts most often side with the employers is a product of the anti-union legal culture encouraged in this country at least since Thatcher, and prolonged under the last Labour government.

But there is one other factor, which is a creeping campaign by employers to extend the practical scope of anti-union laws through precedent-setting cases like these. In several similar cases in the last few years, technicalities relating to balloting have been used to outlaw strikes. For example, BA workers were prevented from striking in 2010, when Willie Walsh was out to bust the union. The same year, signal workers were hit with a similar injunction. And in 2008, Metrobus workers strike was stopped on similar grounds.

In short, the law has been an ally of employers, making up for any potential weakness in their bargaining position with the full force of the state. But there won't always be legal loopholes to exploit, and even the courts sometimes reject egregious petitions for injunction. In this case, moreover, the court's action made little difference – not only because of its limited coverage, but also in part because the consensus for action among the bus drivers was so overwhelming that it would have been difficult to call the action off. In London, the troika of the courts, the administration and the Evening Standard hasn't broken the RMT. And if the administration and the bus companies are going to provoke bus drivers, they may find them to be an even more indomitable opponent.